VOLUME XX OCTOBER, 1941 number 4 



THE BELL SYSTEM 



TECHNICAL JOURNAL 



DEVOTED TO THE SCIENTIFIC AND ENGINEERING ASPECTS 

 OF ELECTRICAL COMMUNICATION 



The Reliability of Holding Time Measurements 



— Roger I. Wilkinson 365 



Electrical and Mechanical Analogies — W. P. Mason . . 405 



The History of Electrical Resonance — Julian Blanchard ,415 



A Rapid Visual Test for the Quantitative Determination of 

 Small Concentrations of Calcitun in Lead 



— Earle E. Schumacher and G. M. Bouton 434 



Abstracts of Technical Articles by Bell System Authors . 439 



Contributors to this Issue 442 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



50c per copy $1.50 per Year 



